When you have strabismus, or crossed eyes, your eyes point in different directions. It might happen sometimes or all the time. While one eye looks forward, the other eye may look inward, outward, up, or down. That means the eyes don't work together to look at objects, causing problems such as blurred or double vision. In some cases, it leads to poorly developed vision in one eye, called amblyopia, or lazy eye.
The condition is most common in children, but if it goes untreated, it can linger into adulthood. Adults with certain medical conditions also can develop strabismus. It affects about 4% of people in the United States.
Doctors describe strabismus by the way it looks or by other features.
Types of strabismus based on appearance include:
- Esotropia: when the eye turns inward
- Exotropia: when the eye turns outward
- Hypertropia: when the eye points upward
- Hypotropia: when the eye points downward
Other ways to descript strabismus include:
- Intermittent or transient: when it only happens sometimes
- Constant: when it happens all the time
- Unilateral: when it's always in the same eye
- Alternating: when it happens in one eye sometimes and the other eye at other times
Doctors may also use more specific terms to describe some common types of strabismus. These include:
- Accommodative esotropia: This happens to people, usually young children, who are farsighted, meaning they see distant objects better than close ones. If the farsightedness isn't corrected, they may work so hard to focus that one or both eyes may turn inward.
- Intermittent exotropia: In this type, one eye sometimes drifts outward while the other stays focused. The eyes may trade off positions or the same eye may wander every time.
- Infantile esotropia: This happens in infants, before age 6 months, without farsightedness. One or both eyes can turn inward.
Strabismus can be caused by problems with the eye muscles, the nerves that send information to the muscles, or the part of the brain that controls eye movement. The cause isn't always clear.
You are more likely to develop it if you have:
- A family history of strabismus. About 30% of children with strabismus have an affected family member, suggesting the condition can be inherited.
- Farsightedness or nearsightedness. Struggling to focus increases the risk.
- Certain medical conditions. Premature birth, Down syndrome, cerebral palsy, hydrocephalus (buildup of fluid in cavities deep within the brain), and other neurological conditions increase the risks. You also can develop strabismus at any age as a result of a stroke, brain tumor, or head injury. Some adults with a thyroid condition called Graves' disease also develop strabismus.
Since strabismus most often starts in children under age 3, including some too young to talk, parents and others may be the first to notice signs such as:
- Eyes that look out of line
- Eyes that don't move together
- Frequent blinking or squinting, especially in bright sunlight
- Tilting the head to look at things
- Closing one eye to look at things
Other symptoms of strabismus can include:
- Double vision
- Trouble reading
- Eye strain
Important to know: it's normal for babies to have wandering eyes from time to time. But by age 3-4 months, their eyes should be straight, well-aligned, and able to focus on small objects. By age 6 months, they should be able to focus on objects that are close and far away.
If an adult or an older child suddenly develops double vision or other signs of strabismus, you should call a doctor right away. It's important to find the underlying cause.
Sometimes, babies with certain facial features look like they have crossed eyes when they really don't. That's called pseudostrabismus. The confusion is most likely when a baby has some extra skin covering the inner corners of the eyes or a flat nose bridge. As the face develops and grows, the baby's eyes will stop looking crossed.
Sometimes possible strabismus is picked up during a child's regular checkups, when health care providers may use a screening test called a corneal light reflex test (Hirschberg test). In this test, the child looks at a colorful object while a bright light is shined in the eyes. The health care provider can see if reflections are the same in each eye.
An eye doctor, called an ophthalmologist, can confirm a diagnosis of strabismus. Some specialize in diagnosing and treating children. The doctor will start by getting a medical history to find out when symptoms started and what other conditions you or your child might have.
Often, the doctor can see that you have strabismus by looking at you. They might also perform a simple test in which you look at an object while covering and then uncovering each eye, to see how and when the abnormal turning happens.
Additional tests could include:
- Visual acuity: This is a test of how sharp or clear your vision is. In the most common version, you read letters from a chart. Eye doctors have different ways of testing visual acuity with young children and others who can't read or understand the eye chart test.
- Refraction: Checking the eyes with a series of lenses. This is the test used to determine eyeglass prescriptions.
- Alignment and focus tests: These look at how well your eyes focus, move, and work together.
- Dilating the pupils: Using eye drops, the doctor may widen the pupils to better see inside the eyes and looks for signs of disease.
Sometimes, doctors order additional tests to understand the underlying causes of strabismus. These might include blood tests and MRI scans of the eye sockets.
It's important to start treating strabismus as soon as you can. That can prevent long-term problems, including poor vision in children that lasts into adulthood. But it's also never too late to treat strabismus, even if you're an adult who's had it since childhood.
Treatment options depend on the underlying cause, the severity, and the person's age. They include:
Glasses or contact lenses
If strabismus is caused by struggling to focus on objects near or far, regular glasses or contact lenses can sometimes solve the problem.
If strabismus is causing double vision, special lenses called prisms might help. The lenses bend the light entering your eye to better line up the images you see. But these special glasses can have bothersome side effects, such as creating colored fringes around objects.
If a child has a so-called lazy eye (amblyopia), meaning weak vision in a frequently misturned eye, doctors sometimes recommend wearing a patch over the better eye. That can help the weaker eye become stronger over time.
As an alternative to a patch, the doctor might prescribe eye drops to cause blurry vision in the better eye until the weaker eye gets stronger. Some other medications may also be tried.
Injections of botulinum toxin (Botox) can temporarily ease eye turning by stopping muscles around the eye from working. One risk is that it can cause a droopy eyelid.
If other treatments don't work, you might get surgery for strabismus. This is mostly an option for children, but adults have it sometimes, too.
In the surgery, usually done under general anesthesia, your doctor makes cuts in the clear membrane over the whites of your eyes. The surgeon then tightens or loosens eye muscles to help the eyes line up better. You might have surgery on one or both eyes.
After moving the muscles, the surgeon will use dissolvable stitches to close the cuts. In some cases, the surgeon will leave adjustable stitches attached to the muscles. These muscles can then be tightened or loosened some more shortly after the surgery, if needed. But this option is usually reserved for adults and teens, since the adjustments are done when you're awake and children might not cooperate.
You might get eye drops or ointment to put on the eyes at home. The eyes can take 3 to 12 weeks to heal.
The surgery sometimes improves appearance without improving vision. And sometimes the eye wandering comes back, despite the surgery. You also face the risks of any surgery, like infection and bleeding.
Strabismus Eye Exercises
In addition to any other treatments, your eye doctor might recommend you see a specialist for eye exercises, also known as vision therapy. These activities are designed to improve eye coordination and focus and to help your brain and eyes work better together. You usually see a therapist called an orthoptist or an optometrist, an eye professional who is not a medical doctor.
You might do some of the exercises in the therapist's office with special lenses, prisms, and computer programs, and some at home, as instructed by the therapist.
These might include:
To do this, you hold a pencil at arm’s length from your face, then slowly move it closer to your nose, following it with your eyes and keeping it in focus. When you start to see two pencils, you move the pencil further away again. You might repeat this several times a day. This treatment alone has not been proven to help strabismus.
This exercise uses colored beads spaced apart on a 5-foot string tied to a stable object like a chair and stretched to your nose. You focus on the bead closest to your nose and then those farther away.
You draw three red barrels, small, medium and large, on one side of a card and three green ones, also small, medium and large, on the other. The barrels should line up lengthwise. You hold the edge of the card against your nose, so you see the red and green sides, with the small barrels closest and the large ones farthest away You stare at the large barrels until they become one image, then repeat with the smaller ones.
If strabismus goes untreated, it can cause additional, lasting problems, including:
- Amblyopia (lazy eye). This happens when the brain constantly gets separate images from the two eyes. To avoid double vision, the brain starts ignoring the image from the wandering eye. In a child, that means normal vision doesn't develop in that eye and it gets weaker.
- Double vision. This is common in adults who develop strabismus because their brains can't ignore images from the wandering eye.
- Blurry vision. This gets in the way of school, work, and other activities.
- Poor three-dimensional (3D) vision. This makes it harder to see how far or near something is.
- Eye strain
- Low self-esteem and embarrassment about how your eyes look
Ignoring strabismus can also mean ignoring the underlying cause. In adults and older children with sudden strabismus symptoms, it could be something serious, like a stroke or a brain tumor.
When your eyes point in different directions, it isn't just a cosmetic problem. Strabismus can seriously harm vision in a developing child and cause problems ranging from blurry vision to embarrassment in people of any age. If you think you or your child might have strabismus, talk to your doctor.
Can glasses fix strabismus in adults?
Eyeglasses fitted with special prism lens can help clear up the double vision that many adults with strabismus have. However, if the glasses don't work or are too heavy or uncomfortable (a common complaint), surgery may be an option.
Is strabismus a visual disability?
Strabismus may be considered a visual disability or impairment (by schools, for example) if the vision problems it causes can't be corrected by glasses or other measures.